At 05.01 hours on 10 June 1942 the unescorted Merrimack (Master Wilbur Flowers) was hit by one stern torpedo from by U-107 about 65 miles southeast of Cozumel Island, south of the Yucatan Channel. The G7a torpedo struck on the starboard side just forward of the bridge and the ship immediately developed a 20° list to starboard. The engines could not be secured and were running at full speed until the ship sank 38 minutes after the hit. All officers, except the master, and 30 other survivors abandoned ship in one lifeboat because the other was destroyed in the explosion. The boat was sucked into the still turning screw and it appears that none of the occupants survived the incident. The men still aboard, including the master, had to jump overboard but only a few managed to reach the rafts that had been released. The master, 34 crew members, eight armed guards and one US Army passenger were lost.

Eight crew members and one armed guard were picked up from two rafts by USS Borie (DD 215) on 15 June in 20°48N/85°30W, after being spotted by a PBY Catalina flying boat. They were taken to Cristobal, arriving on 19 June. An able seaman was picked up from another raft on 15 June by the US Army troop transport Argentina and landed at New York on 20 June.